Positional uncertainties of the recording film are the serious limitations to the geometric accuracy of images recorded in high performance EBRs. One cause of positional uncertainty has been that prior films have been provided with edge perforations or gear slots to permit a gear driven film advance. These edge perforations are formed in the film at the time of manufacture. The accuracy with which these perforated films can be positioned is particularly limited by the degree to which the gear teeth accurately engage the perforations. A cause of misalignment is that charged particle recording films are subject to expansion and contraction due to changes in atmospheric conditions and as a result of film handling and processing. Accordingly, the peforation spacing can change while the gear teeth spacing remains constant. Thus, there is a definite need in the art for means which can accurately reference film and the image applied thereto where the accuracy of said means is not substantially impaired by expansion or contraction of the film.
Although prior film referencing means have been provided, none has overcome the problems associated with film expansion and contraction and the impairment of the accuracy of the reference means in EBR's. Although prior EBR systems provided by the inventor have employed film punches for piercing reference holes in the perimeter of the image field, these reference holes, after film expansion or contraction, often do not match up with the display means alignment peg and consequently the film can buckle with the resultant distortion to the film image. In some cases the non-alignment will cause the image reference holes to be damaged.